﻿SPERMATOGENESIS 
  OF 
  PEBlPLANETA 
  AMERICANA. 
  5*77 
  

  

  pail- 
  of 
  rounded 
  masses. 
  As 
  the 
  two 
  parts 
  separate 
  aud 
  move 
  

   to 
  opposite 
  poles 
  of 
  tlie 
  spindle, 
  a 
  straud 
  of 
  their 
  substance 
  

   remains 
  as 
  a 
  connecting 
  link 
  for 
  some 
  time, 
  giving 
  them 
  the 
  

   appearance 
  of 
  a 
  number 
  of 
  dumb-bells 
  (fig. 
  24'). 
  

  

  Throughout 
  the 
  homotype 
  prophase 
  no 
  structure 
  resembling 
  

   a 
  nucleolus 
  has 
  appeared 
  in 
  the 
  nucleus, 
  but 
  the 
  remains 
  ot 
  

   the 
  heterotype 
  nucleolus 
  still 
  persist 
  in 
  the 
  cytoplasm 
  (tigs. 
  

   19—25). 
  

  

  The 
  reconstructed 
  nuclei 
  of 
  the 
  daughter 
  cells, 
  produced 
  

   by 
  the 
  homotype 
  division, 
  present 
  at 
  first 
  a 
  dense, 
  highly- 
  

   chromatic 
  appearance. 
  An 
  intermediate 
  body 
  (cf. 
  Flemming) 
  

   persists 
  for 
  some 
  time, 
  attached 
  to 
  which 
  are 
  the 
  collapsed 
  

   remnants 
  of 
  the 
  spindle, 
  and 
  these 
  finally 
  separate 
  aud 
  form 
  

   an 
  elliptical 
  or 
  rounded 
  mass 
  of 
  dense 
  cloudy 
  cytoplasm, 
  the 
  

   nebankern, 
  a 
  structure 
  which 
  probably 
  takes 
  part 
  in 
  the 
  con- 
  

   struction 
  of 
  the 
  cephalic 
  vesicle, 
  aud 
  the 
  tail 
  of 
  the 
  sperma- 
  

   toiioon 
  (figs. 
  25 
  — 
  27). 
  

  

  The 
  outer 
  system 
  of 
  the 
  homotype 
  spindle-elements, 
  as 
  

   described 
  by 
  one 
  of 
  us 
  in 
  Elasmobrauchs, 
  is 
  also 
  often 
  per- 
  

   ceptible 
  (fig. 
  26). 
  

  

  The 
  Spermatid. 
  — 
  The 
  nucleus 
  of 
  the 
  daughter 
  cell 
  or 
  

   spermatid 
  rapidly 
  loses 
  its 
  dense 
  appearance 
  (fig. 
  27), 
  the 
  

   chromatin 
  gradually 
  breaking 
  down, 
  aud, 
  as 
  this 
  proceeds, 
  a 
  

   well-defined, 
  spherical, 
  chromatic 
  body 
  becomes 
  visible 
  in 
  the 
  

   nucleus. 
  It 
  is 
  smaller 
  in 
  size 
  than 
  either 
  of 
  the 
  previously 
  

   described 
  nucleoli, 
  in 
  proportion 
  to 
  the 
  reduced 
  size 
  of 
  the 
  

   nucleus 
  in 
  the 
  spermatid. 
  

  

  The 
  nuclear 
  contents, 
  at 
  this 
  stage, 
  consist 
  of 
  a 
  coarse 
  

   reticulum 
  of 
  liniu 
  (fig. 
  28), 
  suspended 
  in 
  which 
  are 
  the 
  

   rapidly-disappearing, 
  rounded 
  masses 
  of 
  chromatin. 
  At 
  this 
  

   stage 
  the 
  chromatic 
  body 
  or 
  nucleolus 
  of 
  the 
  spermatid 
  (/«.'", 
  

   figs. 
  28 
  — 
  31) 
  is 
  seen 
  to 
  lie 
  in 
  contact 
  with 
  the 
  nuclear 
  mem- 
  

   brane, 
  forming 
  a 
  very 
  conspicuous 
  object 
  in 
  the 
  nucleus. 
  

  

  The 
  coarse 
  reticulum 
  gradually 
  breaks 
  down 
  into 
  a 
  finer 
  

   structure, 
  still 
  supporting 
  a 
  few 
  minute 
  granules 
  of 
  chromatin. 
  

   The 
  nucleolus 
  now 
  undergoes 
  fissure 
  (tig. 
  81), 
  one 
  half 
  remains 
  

  

  